iKnowthat.com has online multimedia educational games for kids in grades PreK through 6 (ages 2-12).

Music Maker Game

The Music Maker game lets kids compose and listen to their own compositions.  Or, kids can listen to more than 15 sample songs.  With the Music Maker activity, kids can explore different rhythms, patterns, and tempos.  They can learn basic music notation and practice reading music.  Music Maker has a variety of instruments and sound effects for playing compositions. Kids can save their compositions at iKnowthat.com and share them with others.